The present invention relates to wound drain catheters for draining fluid from, or supplying medication to, a wound.
Virtually all wound drain catheters presently used in closed wounds comprise a drain section for fluid communication with the wound and a separate outflow or extension tube section for carrying the fluid between the drain section and a reservoir. Typically, the drain section of a wound drain catheter comprises a length of tubing that is perforated by forming small apertures through the tubing wall. Several problems accompany this type of structure for the drain portion of the wound drain catheter. These problems are discussed in applicant's co-pending application, Ser. No. 238,640, filed Feb. 26, 1981. In that application a new type of drain section for a wound drain catheter is disclosed. This new type of drain section is formed of a silicone elastomer and comprises a fluted main body having longitudinal lumens open to the wound surrounding the drain portion. The advantages of a drain of this design over the drains of the prior art include an increased lumenal flow drainage area, elimination of stress points in the drain section that may lead to breakage of the drain as it is removed from the patient's body, and reduction of the risk that tissue growth will inhibit removal of drain.
Nevertheless, the drain portion there disclosed must be attached to a separate outflow tube. A butt joint is formed between the ends of the drain and the tube, with the two portions connected by an exterior collar. To ensure that the collar does not close the ends of the lumens of the drain portion, prohibiting fluid flow from the drain to the outflow tube, the end of the drain portion is undercut to provide a semi-spherical recess for fluid communication between the lumens and the outflow tube. This joint between the drain portion and the outflow tube establishes a point at which the strength of the drain catheter might be reduced, thus creating the possibility of breakage during removal of the drain from the patient's body. The collar, which necessarily has an outer diameter larger than the diameter of the drain portion and the extension tube portion, may provide added resistance to removal of the catheter. Although the possibility of this collar binding on material as it is pulled through the body is remote, the segment of increased diameter may give rise to added friction between the drain and the flesh surrounding it as the drain is pulled out of the body. In addition, forming the semi-spherical recess in the drain portion and attaching the drain portion to the outflow tube require additional steps during the manufacture of the catheter, making manufacture more time-consuming and expensive than the manufacture of a single piece catheter in a single process. Thus, while the drain catheter disclosed in patent application Ser. No. 238,640 substantially improved upon the prior art, room for further improvement remained.
The dies presently used in the extrusion of silicone or plastic materials comprise a die nozzle having a die cavity from which a parison is extruded. The die cavity has fixed within it die forms and/or die mandrels, around which the material flows as it is extruded from the die cavity to form a parison of the desired shape. Most of the die forms and die mandrels of the dies presently in use are fixed in place within the die cavity during the extrusion process. A few devices have a central die mandrel that has limited linear movement to vary the wall thickness of a tubular parison. But, to change the shape of the parison, the extrusion process must be halted, the dies moved or changed, and the extrusion process begun again. Consequently, changes of the parison shape are not possible in a single, continuous parison, so the parison extruded during a single extrusion is necessarily of uniform cross section. This limitation on the extrusion process has required the separate manufacture of the drain section and the extension tube section of wound drain catheters. In particular, with reference to applicant's co-pending application Ser. No. 238,640, the fluted drain section and the extension tube section of the wound drain catheter therein disclosed have necessarily been formed as separate pieces and joined together in a later process.